It is highly desirable for tires to have good wet skid resistance, low rolling resistance and good wear characteristics. It has traditionally been very difficult to improve a tire's wear characteristics without sacrificing its wet skid resistance and traction characteristics. These properties depend, to a great extent, on the dynamic viscoelastic properties of the rubbers utilized in making the tire.
In order to reduce the rolling resistance and to improve the treadwear characteristics of tires, rubbers having a high rebound have traditionally been utilized in making tire tread rubber compounds. On the other hand, in order to increase the wet skid resistance of a tire, rubbers which undergo a large energy loss have generally been utilized in the tire's tread. In order to balance these two viscoelastically inconsistent properties, mixtures of various types of synthetic and natural rubber are normally utilized in tire treads. For instance, various mixtures of styrene-butadiene rubber and polybutadiene rubber are commonly used as a rubbery material for automobile tire treads.
U.S. Pat. No. 6,103,842 and U.S. application Ser. No. 10/124,006, now U.S. Pat. No. 6,627,715, disclose processes and catalyst systems for the copolymerization of 1,3-butadiene monomer and styrene monomer into a styrene-butadiene copolymer having a high trans-1,4-polybutadiene content and having a random distribution of repeat units which are derived from styrene. It is also therein disclosed that styrene-butadiene rubber made utilizing the catalyst system and techniques therein may be used in the preparation of tire tread rubber compounds which exhibit improved wear characteristics. What is not disclosed is that superior wear characteristics may be obtained using a low styrene content in the high trans random SBR.